Protective apparatus



J. BIERMANNS PROTECTIVE APPARATUS Filed April 11, 1924 2 Sheets-Shoot 1 March 17, 1925. 1,530,291

/5 /3 J /2 I a H i s fittorn e y.

March 17, 1925-,

J. BIERMANNS PROTECTIVE APPARATUS Filed April 11, 1924 -2 Sheets-Sheet 2 Inventor:

Josef Biermanns by W% His Attorney.

Patented Mai-.17, 1925.

UNITED STATES PATENT orrlcs.

JOSE? BIER I'ANNS, OF KARLSHORST, GERMANY, ASSIGNOR T ELECTRIC COMPANY, CORPORATION OF NEW YORK.

PROTECTIVE APPARATUS.

Application mm April 11, 1924. Serial No:'705,861.

Y '0 all whom it may concern Be it known that I, Josnr BUJRMANNS, a citizen of Germany, residing at Karlshorst, Germany, have invented certain new and useful Improvements in Protective Apparatus, of which the followingis a specification.

My invention relates to improvements in protective apparatus for electric systems,

D and more particularly to improvements in relays for selectively controlling the circuits of parallel lines upon the occurrence of abnormal circuit conditions. V

In Letters Patent of Germany, No. 349,753, 5 March 9, 1922, there is disclosed a relay for selectively controlling the circuits of a plurality of parallel lines in accordance with the sum of and difi'erence between the currents in the lines upon the occurrence of an unbalance in the currents thereof. In normal operation, that is, assuming for ex ample, two parallel lines carrying equal currents, the dlfierence between the currents is substantially zero and the relay is not actu- 5 ated'.- Upon the occurrence of a diflerence between thecurrcnts, the relay operatesse lectively tocontrol the circuit of the line, carrying for example, the greater current. Under certain conditions, for example, a fault causing a reversal of power in one of the lines, the current in one line becomes reversed relatively to the current in the other line so that, if the currents areequal, their sum is substantially zero and the relay would not be actuated. It is an ob'ect of my invention to provide an improve relay w ose operation is dependent not only upon the sum of and the difference between the currents in two parallel lines, but also u on I the voltage of the sy'stemto which the lines are connected and the difference between the currents in the lines, so as to assure a positive and selective relay operation even though the current in one lmeis reversed i latively to the current in the other line and t e currents are equal.

My invention will be better understood from, the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

Fig. 1 illustrates partly in diagram and perspective an embodiment of my invention, and Fig. 2 illustrates a modification of my invention.

Figs. 1 and 2 show a part of a three-phase alternating current electric systemcomprising two parallel lines 1 and 2 connected to a common bus 3, and a relay 4 embodying my invention and comprising a movable contact controlling member 5 arranged selectively to control contacts'G and 7 in the control circuits of tripping devices 8 and 9 respectively, whereby the automatic opening of suitable circuit breakers lO'and 11 in the lines 2 and 1 respectively canbe selectively controlled upon the occurrence of an unbalance in the line currents.

The relay 4 is of the so-called watt or power type and comprises a winding 12 connected to be energized in accordance with the voltage of the system, a winding 13 connected to be energized in accordance with the difference between the currents in the lines 1 and 2 'and a winding 14 connected to be energized in accordance with the sum of the currents inthe lines. The windings 12, 13 and 14 are arranged to. produce a turning moment or torque which is substantially proportional to the product of the sum of the voltage of the system and the sum of the currents 1n the two lines, and the difference between the currents in the line. This may be expressed mathematically substantially as follows .where T is the torque, K a constant, E the voltage of the system, I and I the currents in correspondin phase conductors of-the linesl and 2 an E and I or 1,.

- The relay '1 may be of the induction power type and, as illustrated, comprises a rota-' ta ly mounted conducting member such as a disk 15 by the movement of which the contact controlling member 5 is actuated. In order that the movement of the disk 15 may be controlled by the torque of the windings 12, 13 and 14, these windings are mounted on ma netic members or cores 16 and 17 between the pole faces of which the disk 15 '9 the phase angle between is interposed so as to be rotatable across the magnetic field of the cores. with their associated windings thus constitute an electromagnetic means or motor element whereby the disk 15 is actuated in a well known manner.

As shown in Fig. 1, the winding 14 is mounted on the core 17 and connected across a circuit including the secondaries of-current transformers 18 and 19 in correspond ing phase conductors of the lines 2 and 1 respectively. These transformers are connected for opposing electromotive forces assuming that the direction of power in each line is the same. Consequently, the sum of the currents in corresponding phase conductors of the lines 1 and 2 flows throu h the whole of the winding 14, and this win ing is energized in accordance with the sum of the currents in the lines. The winding 13 is mounted on the core 16 and connected across normally equipotentialpoints in a circuit including the secondaries of current t-rans-' formers 20 and 21 incorresponding phase conductors of the lines 2 and 1 respectively.

These transformers are connected for circulatmg current, assuming that the direction of power in each line is the same. Consequently, the difference between the currents in corresponding phase conductors of the lines 1 and 2 flows through the winding 13. In order that the windings 13 and 14 may cooperate-to exert a torque on the disk 15, the fluxes generated by the currents in these windings must be displaced in phase. For

. this purpose, any suitable phase displacing means such as a resistance 22 in parallel with the winding 13 may be used. The windings 13 and 14 thus cooperate to exert onthe dish a torque substantially proportional to the product of the sum of and the difference between the currents in corresponding phase conductors of the lines 1 and 2 or in other words, proportional-to the difference in the squares of the currents. This may be expressed mathematically substantially as follows: I

T1=K(I1+I2) i It will be observed that this equation for torque represents a portion of the torque expressed in equation (1).

In order to reduce the number of current transformers employed, the cooperating current windings 13 and 14 may be connected as shown in Fig. 2. En this modification, the winding 13 is connected across normally equipotential points in a circuit including the secondaries of current transformers 23 and 24 in corresponding phase conductors of the lines 1 and 2. This circuit includes the winding 14 in series with thesecondaries of the current transformers 23 and 24, which are "connected for circulating current assuming that the direction of power each line These cores cordance with the difference between the currents in the lines 1 and 2. T sum of the currents in the lines 1 and 2, owever, does not flow in the whole of the winding 14, but substantially one-half of the winding is energized by the current of one line and the I other half by the current in the other line. The winding 14 is therefore in effect, energized in accordance with the sum of the currents in the lines since the ampere-turns are substantially equal to the product of onehalf of the number of turns in the winding and the sum of the currents in the lines. In order that the windings 13 and '14 may cooperate to exert a torque on the disk 15, the fluxes generated by the currents in these windings must be displaced in phase. F or,

this purpose, any suitable phase displacing means such as a resistance 25 in parallel-with the winding 14 may be used. The windings 13 and 14 then cooperate to exert a torque substantially proportional to the product of the sum of and difference between the currents in the lines 1 and 2 as expressed in equation (2).

In order to prevent undue oscillations of the disk 15 upon a small unbalance in line currents, suitable damping means such as the drag magnet 26shown in Fig. 2 may be provided.

The voltage winding 12 is mounted on the core 17 and connected in circuit with the bus 3 through a potential transformer 27. This winding is therefore energized in accordance with the voltage of the system. and is arranged to cooperate with the winding 13 in controlling the movement of the disk 15. In a three-phase system the so-called quadrature connection is preferably employed,

that is to say, if the current winding 13 is IOU winding 12 may be used; The windings 12 and 13 therefore cooperate to exert on the disk 15 a torque which is substantially proportional to the product of the voltage of the system, the difference between the currents in corresponding phase conductors of the; lines 1 and 2, and a function of the phase angle between the voltage and the difference between the 'line currents. This may be expressed mathematically substantially as follows It will be observed that this equation. for torque represents a portion of the torque expressed in equation (1) and that the combined torque of the three windings is equal to the sum of the torques expressed in equations (2) and (3), as expressed in equa; tion (1).

The voltage winding 12 is preferably arranged relatlvely to the current winding 14.- so that with power in both of the lines 1 and 2 flowing from the bus 3 to'the lines land 2, the flux generated by the current in the voltage winding 12 assists the flux generated b the current in the current winding 14. eefl'ect of these windings combined with the efl'ect of the current winding 13 assures a positive and selective relay action at all times, for although the sum of the line currents may be zero, there remains a torque, as expressed in equation (3), which is ef fective to actuate the disk 15. i

a The disk 15 and contact controlling member 5 associated therewith are biased to a position such that the member 5 is normally intermediate the contacts 6 and 7. For this purpose, any suitable biasing means such as a s ring 29 may be used.

or simplicity, I have shown in Figs. 1

and 2 my invention as applied to only one phase of a three-phase alternating current electric system, but the application of my invention to the other phases of the system or to systems other than three-phase will be apparent to thoseskilled in the art. In some systems, it may be that the parallel lines do not normally carry equal currents. In this case, the transforming ratios of the current transformers may be arranged so that the outputs of their secondaries are equal under normal line conditions.

Referring now to equation (1) and assuming that the currents in the lines 1 and 2 are substantially equal and that the direction of power in each line is the same, it is obvious that there will be no torque to actuate the disk 15, since the difierence between the line-currents is substantially zero. Assuming now that there is an unbalance in the currents in the lines 1 and 2 and that power flows from the bus 3 to each of the lines, it is obvious that the direction of the torque is determined by the relative values of the line currents, that is to say, by the dilference between the currents; Consequently, the rela is operative upon the occurence of an un alance in the line currents 1 selectively to control the circuit of the line carrying, for example, the greater current. Assuming a fault causing an unbalance in the line currents and that power flows from current. Upon the occurrence of a fault causing a reversal of power in one of the lines, the fault currents in the lines may be equal and consequently the sum of the ourrents would be substantialy zero so that the torque as expressed in equation (2) would not be effective to actuate the disk 15. In

this case there remains, however, the torque as expressed in equation (3). The direction of this torque being determined by the relative directions of power in the lines 1 and 2*, that is to say, the sign of the factor (I I,, it is obvious ihat the relay is operative selectively to control the circuit of the line in which the reversal of power has occurred.

It will be apparent to those skilled in the art that many modifications and variations may be made within the scope of my invention which is not limited to the particular construction of relay disclosed and I, therefore, aim in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an electric system of the class described wherein a plurality of lines are connected in parallel and wherein means are provided for, selectively controlling the circuits of said lines comprising a relay provided with a winding connected to be .energized in accordance with thevoltage of the system and a winding connected to be ener- 1 gized in accordance with the difl'erence between the currents in said lines,' the combination with said windings of a winding connected to be energized in accordance with the sum of the currents in said lines.

2. In an electric system comprising a plurality of arallel lines, means for selectively' contro g the circuits of said lines upon the occurrence of an unbalance in the currents thereof comprising a movable member, electromagnetic means for actuating said member comprising a plurality of cooperating windings, one of said wind being connected to be energized in acco ance with the difference between the currents in said lines, another of said windings being connected to be responsive to the voltage of the system, and another of said windings being connected to be energized in accordance with the sum of the currents in said lines.

3. In an electric system comprising a plurality of parallel lines, means for selectively controlling the circuits of said lines upon the occurrence of an unbalance in the currents thereof comprising a movable mmber, electromagnetic means for actuating said member comprising a plurality of co operating current and voltage windings connecte and arranged to exert on said member an efl'ect substantially proportional to the product of the sum of the voltage of the system and the currents in two of-said lines and the dilference between the currents in said two lines. 4

4. In an electric system'comprising a plurality of parallel lines, means for selectively controlling the circuits of said lines upon the occurrence of an unbalance in the currents thereof comprising a rotatable conducting member and electromagnetic means for actuating said member inductively associated therewith and comprising one voltage and two current cooperating windfngs, saidcurrent windings being connected in circuit with said lines tobe energized, one in 'accordance with the sum of and another in accordance with the difierence between the currents in the lInes, and said voltage winding being connected in circut with said system to be energizedin accordance with the voltage thereof. v

5. In an electric system comprising a plurality of parallel lines, meansfor selectively controlling the circuits of said lines comprising a relay having a plurality of windings connected in circuit with said lines, one to be energized in accordance with the sum of and anotherin accordance with the difference between the currents in the lines characterized by the fact that the relay comprises a winding connected in circuit with said system to be energized in accordance with the voltage thereof and arrangedto cooperate with the winding energized by the difference between the currents upon the occurrence of a fault causing a' reversal of power in one ofsaid lines.

6. In an electric system comprising a plurality of parallel lines, means tor selectively controlling the circuits of said lines upon the occurrence of an unbalance in the currents thereof comprising a relay having a plurality of energizing windings, means connecting two of said windings to the sys tem whereby the efi'ect of the two windings is dependent on both the sum of and the difference between the currents in, two of said lines, characterized b the fact that the relay comprises a win ing connected in circuit with the system to be energized in accordance with the voltage thereof and ar-' ranged to supplement the effect of said two windings upon the occurrenceof a reversal of power in one of said lines.

7. In an electric system comprising a pluralty of parallel lines,means for selectively controlling the circuits of said lines comprising an induction relay having a rotatj able conducting member and means for actuating said member comprising two cooperating current windings connected in circuit with said lines to be energized, one

in accordance with the sum ofand-the other 7 in accordance with the difference between the currents in said lines and arranged to exert on said member a torque substantially proportional to. the difi'erence between the squares of the currents in said lines, and a voltage winding connected to be energized in accordance with the voltage of the system and arranged to cooperate with said a other current winding to exerton sald memher a torque substantially proportional to the product of the voltage of the system and the difference betweenthe currents insaid lines.

In witness whereof, I have hereunto set my hand this 25th day of March,1924.

' JQSEF BIERMANNS. 

